RU2245388C1 - Aluminum-based material - Google Patents

Abstract

FIELD: aluminum metallurgy.

SUBSTANCE: claimed material contains zinc, magnesium and nickel and has structure consisting matrix formed from aluminum solid solution with homogeneously dispersed particles of secondary precipitates and homogeneously dispersed particles of crystal-originated nickel aluminide In particular material contains (vol %): nickel aluminides 5.3-7.0, and balance: matrix. Matrix as dispersed particles of secondary precipitates contains 6-10 vol % of phase T' particles being metastable modification of T(Al₂Mg₃Zn₃) phase with average diameter not more than 50 nm and equilibrium solidus temperature not less than 540⁰C. In particular embodiment of invention material contains globular nickel aluminides with average diameter not more than 5 mum. Material has Brinell hardness at least 160 and is made in form of castings having ultimate resistance of ς_B at least 510 MPa, yield strength ς_0.2 at least 420 MPa, aspect ratio δ at least 4 %. Material also may be made in form of strained half-staffs having ultimate resistance of ς_B at least 570 MPa, yield strength ς_0.2 at least 480 MPa, aspect ratio δ at least 5 %. Material of present invention is useful in product manufacturing, operated at 150-200⁰C.

EFFECT: new material capable to heat hardening with improved mechanical characteristics.

5 cl, 3 tbl, 2 ex

Description

The invention relates to the field of metallurgy of aluminum-based materials and can be used to obtain products operating under high loads at temperatures up to 150-200 ° C, such as parts of cars and other vehicles (bicycles, scooters, trolleys), sports equipment parts and other

Wrought thermally hardenable aluminum alloys based on the 1915 Al-Zn-Mg system (GOST 4784-75) have a successful combination of processability (by pressure treatment, weldability), corrosion resistance and mechanical properties (Industrial aluminum alloys / Ed. Ed. / Alieva S .G., Altman MB and others M .: Metallurgy, 1984. 528 p.).

They have medium strength (σ _in = 300-400 MPa), since the total content of magnesium and zinc in them does not exceed 6-7%. With an increase in this value, the strength increases, however, the alloys become sensitive to intergranular fracture, which negatively affects ductility, fatigue properties, fracture toughness, and also stress corrosion resistance.

The disadvantage of alloys based on the Al-Zn-Mg system is a high tendency to form hot cracks during solidification, which complicates their use for producing shaped castings of a relatively complex shape.

B95 alloys based on the Al-Zn-Mg-Cu system (Industrial aluminum alloys / Ref. Ed. / Alieva S.G., Altman MB and others) have higher strength (σ _in = 500-600 MPa). M .: Metallurgy, 1984. 528 p.), However, their casting properties are even worse than that of alloys without copper, therefore alloys based on this system are practically not used as casting.

The closest material to the proposed is the material disclosed in patent RU 2158780, 10.11.2000.

This material contains a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with uniformly dispersed dispersed particles of phases formed by aluminum, zinc, magnesium and copper, particles of nickel aluminides of crystallization origin uniformly distributed in the matrix, and at least particles uniformly distributed in the matrix , one of the aluminides selected from the group consisting of chromium aluminides and zirconium aluminides, with a total content of from 0.1 to 0.5 vol.% material.

Castings with improved casting and mechanical properties can be obtained from this material due to the addition of nickel, which forms aluminides of eutectic origin, as well as chromium and zirconium.

However, to achieve high strength properties, it is necessary to provide these aluminides with a globular shape, which requires a spheroidizing annealing operation. Since copper, which is part of the known material, greatly reduces the equilibrium solidus (for the average composition it is below 520 ° C), a relatively high dispersion of the initial structure is required, which limits the use of the proposed alloy to relatively small castings of simple shape. Since ingots intended for the production of deformable semi-finished products have relatively large sizes, the cooling rate in them is usually lower than 2 K / s. Therefore, the use of the material specified in patent RU 2158780, as deformable is difficult. In addition, the presence of copper in the latter reduces the ductility during pressure treatment. It should also be noted that the presence of zirconium and chromium complicates the production of castings and ingots, as during crystallization, primary crystals of aluminides (Al ₃ Zr and Al ₃ Cr) can form, which negatively affects the final mechanical properties. The presence of Zr and Cr additives requires a relatively high casting temperature (more than 730 ° C), which can lead to the burning of magnesium and zinc.

The objective of the invention is the creation of a new material capable of thermal hardening, intended both for producing shaped castings and deformed semi-finished products (from an ingot) having high mechanical properties (not lower than that of alloys of type B95).

The problem is solved in that the aluminum-based material containing zinc, magnesium and nickel, characterized by a structure that is a matrix formed by a solid solution of aluminum with uniformly distributed dispersed secondary precipitates of the hardening phase, and particles of crystallization-derived nickel aluminides uniformly distributed in the matrix, contains a matrix and aluminides in the following ratio, vol.%:

Nickel Aluminides 5.3-7

Matrix rest,

the matrix as dispersed particles contains 5-10 vol.% particles of the phase T ', which are metastable modifications of the phase T (Al ₂ Mg ₃ Zn ₃ ) with an average size not exceeding 50 nm, and the temperature of the equilibrium solidus of the material is not less than 540 ° C.

In private embodiments of the invention, the problem is solved in that the material contains nickel aluminides of globular shape with a size not exceeding 5 microns.

In addition, the material is characterized by Brinell hardness of at least 160 HB.

The material can be made in the form of castings having the following tensile properties: temporary resistance (σ _in ) - not less than 480 MPa, yield strength (σ _0.2 ) - not less than 420 MPa, elongation (δ) - not less than 4% .

In addition, the material can be made in the form of deformed semi-finished products with the following tensile properties: temporary resistance (σ _in ) at least 510 MPa, yield strength (σ _0.2 ) at least 480 MPa, relative elongation (δ) at least 5 %

The invention consists in the following.

The presence of nickel aluminides in the claimed limits (quantity, size and morphology) allows us to provide the best combination of mechanical and technological properties. The presence of phase T 'in the claimed range allows you to provide the necessary level of strength. The lower content of this phase does not allow significant hardening after aging (according to T6 mode). At a higher T 'content, ductility decreases. In this case, the formation of continuous grain-boundary chains (of any phases) is excluded, since they lead to aggravation. The claimed limitation on the temperature of the equilibrium solidus allows spheroidizing annealing at sufficiently high temperatures, providing the formation of relatively globular particles of nickel aluminide.

All of the above is satisfied by materials obtained from aluminum-based alloys containing zinc 5-8, magnesium 2-4 and nickel 3-5.

EXAMPLE 1

Six alloys were prepared, the compositions of which are listed in Table 1. Alloys were prepared in an electric resistance furnace in graphite chamotte crucibles from aluminum of grade A99 (with a purity of 99.99%), zinc of grade C0 (99.9%), magnesium of grade Mg90 (99.9%), copper M1 (99.9%) and alloys Al-20% Ni and Al-10% Cr. The casting temperature of the alloys was 710–730 ° C, the structural characteristics (Q ₁ , Q ₁ , d ₁ , d ₁ and T _s ) and equilibrium solidus (T _s ) (Table 1) were determined on samples cut from heat-treated castings obtained casting into molds with a cooling rate (V _c ) of about 1 K / s. Castings were heat treated according to T6 mode (quenching heating, quenching in cold water and aging). The maximum heating temperature for quenching was maintained 10 ° C below T _s , and aging was carried out at 160 ° C. The equilibrium solidus was determined by differential thermal analysis, and the structure characteristics according to the X-ray spectral and X-ray diffraction analyzes, as well as electron microscopy (scanning - SEM and transmission - TEM). Alloys of close composition with known values of Q ₁ , Q ₁ , d ₁ , d ₁ and T _{s were} used as standards.

Table 1 Composition and structure parameters of experimental alloys No. Zn,% Mg,% Ni,% Other Al Q ₁ ¹⁾ , vol.% Q ₂ ²⁾ , vol.% D ₁ ³⁾ , μm d ₂ , ⁴⁾ nm T _s ⁵⁾ ° s 1 5 1,5 2 - rest 3.2 5,0 <5 <50 602 2 6 1.8 3.2 - 5.3 6.0 <5 <50 585 3 7 2.1 3,7 - 6.1 8.3 <5 <50 570 4 8 2,4 4.2 - 7.0 10.0 <5 <50 545 5 nine 3,5 5 - 8.4 10.5 > 5 > 50 475 6 6 2 4 l% Cu, 0.15% Cr 6.1 7 > 5 <50 525 ^{1) the} volume fraction of nickel aluminides (Al ₃ Ni); ^{2) the} volume fraction of secondary precipitates (in alloys 1-5 of the T 'phase, in the 6-η'alloy); ^{3) the} average size of nickel aluminides; ^{4) the} average size of the secondary secretions; ^{5) the} temperature of equilibrium solidus.

From table 1 it is seen that only the inventive alloy (compositions 2-4) provides the required values of Q ₁ , Q ₁ , d ₁ , d ₁ and T _s . In alloy 1, the number of phases is less than the required level, and in alloy 5, on the contrary, more. In addition, alloy 5 has a low T _s .

In the prototype alloy 6, the equilibrium solidus is at an unacceptably low level, so spheroidizing annealing does not allow to obtain globular inclusions of nickel aluminide with a size of less than 5 microns.

A typical structure of the inventive alloy in casting heat-treated according to T6 mode is shown in the drawing, where a is SEM (casting), b is TEM (sheet).

Mechanical properties in castings were determined on cylindrical samples according to GOST 1497-84.

From table 2 it is seen that alloys 2-4 are significantly superior to alloy 1 in strength properties, and alloys 5 and 6 in ductility.

table 2 Mechanical properties of experimental alloys in castings No. ¹⁾ σ _in , MPa σ _0.2 , MPa δ,% HB 1 325 220 eighteen 120 2 510 420 eleven 162 3 560 485 6 175 4 580 510 4 186 5 310 310 0 210 6 510 480 1 175 ¹⁾ according to table 1

EXAMPLE 2

Prepared 2 mm sheets using technology, which included the following operations:

- obtaining a flat ingot with a cooling rate (V _c ) of about 1 K / s,

- homogenization annealing at a maximum heating temperature of 10 ° C below T _s ,

- hot rolling with a compression ratio of about 90%,

- heating for hardening,

- quenching in cold water,

- aging at 160 ° C.

Table 3 Mechanical properties of experimental alloys in sheets No. * σ _in , MPa σ _0.2 , MPa δ,% HB 1 360 260 fifteen 135 2 570 480 eleven 175 3 590 510 8 185 4 610 530 5.5 200 5 rolling cracks 6 rolling cracks ¹⁾ according to table 1

The mechanical properties in the sheets were determined in the longitudinal direction on flat samples according to GOST 11701-84. From table 3 it follows that alloys 2-4 are significantly superior to alloy 1 in strength properties, the rest in mechanical properties. It should be noted that alloys 5 and 6 do not provide a high-quality sheet, because cracks form during rolling.

Claims (5)

1. An aluminum-based material containing zinc, magnesium and nickel, characterized by a structure consisting of a matrix formed by a solid solution of aluminum with uniformly distributed dispersed particles of secondary precipitates, and particles of crystallization-derived nickel aluminides uniformly distributed in the matrix, characterized in that it contains a matrix and aluminides in the following ratio, vol.%: Nickel Aluminides 5.3-7.0 Matrix Else the matrix as dispersed particles of secondary precipitates contains 6-10 vol.% particles of phase T ', which is a metastable modification of phase T (Al ₂ Mg ₃ Zn ₃ ) with an average size not exceeding 50 nm, and the temperature of the equilibrium solidus of the material is not less than 540 ° C. 2. The material according to claim 1, characterized in that it contains globular-shaped nickel aluminides with an average size not exceeding 5 microns. 3. The material according to claim 1 or 2, characterized in that it is characterized by Brinell hardness of at least 160 HB. 4. The material according to any one of claims 1 to 3, characterized in that it is made in the form of castings having the following tensile properties: temporary resistance σ _in - at least 510 MPa, yield strength σ _0.2 - at least 420 MPa, relative elongation δ - not less than 4%. 5. The material according to any one of claims 1 to 3, characterized in that it is made in the form of deformed semi-finished products having the following tensile properties: tensile strength σ _in - at least 570 MPa, yield strength σ _0.2 - at least 480 MPa, elongation δ - not less than 5%.